Field of Invention
The present invention relates to an improvement in a detecting unit for selecting, at will, a desired sound track of a gramophone record in an automatic tune selection apparatus. Such apparatus is intended for automatically selecting and playing, by means of a detecting unit mounted in a pick-up, using a light source and photoelectric element, a desired sound track from a plurality of the recorded bands of a long playing gramophone record.
Such devices have been introduced by Morton Stimler in his U.S. Pat. No. 2,952,464 and by Tadahiko Nakagiri et al in their U.S. Pat. No. 3,368,080. However, both of said proposed devices have identical shortcomings as will be described below, and therefore, they all lack the reliability desired in such apparatus.
It is often the case that a record player is employed for social gatherings, and it is often placed in a room or a hall under a strong and bright room lighting employed for indoor parties, or in a glary sunny garden used for garden parties. Assuming such bright lighting conditions as described above, the pick-up of a record player equipped with a light projector and a photoelectric element which scans a record, on its way toward a second band where there is music preselected by a selection system of the player, as shown in FIG. 2 of the drawings of the present invention, will no doubt be subject to some of the unwelcomed strong light rays of the room lighting or sun rays as described above other than that of its own light source, which are incidentally reflected from the unmodulated portions preceding the first and second sound track. These rays will be readily absorbed by the sensitive photoelectric elements, thereby incidentally causing misconduct of the selection system and further resulting in an unscheduled landing of the pick-up on a wrong sound track.
One other device that has been proposed by J. Andresen in his U.S. Pat. No. 2,732,539 which is no exception in respect of the shortcomings above-described. Moreover, with its light-luring lens (10 as shown in FIG. 1 of the drawings of his invention) in abutting relation with the sensitive photoelectric cell exposed forwardly and outwardly, it would easily be actuated incidentally by mere headlights of other vehicles passing by, thereby causing failure in its intended purposes.